Correlation Between Ozone Pollution Status And Natural Ozone Stress In Baoding City And The Rhizosphere Soil Of Peony

Ozone（O₃）is the most significant air pollutant on plant growth,but there are few studies on the effects of natural O₃stress on plants.In order to clarify the actual ecological effect of O₃pollution on naturally growing plants,this paper takes the natural growth of peony in Baoding urban area as an example to conduct related research.Firstly,the O₃pollution situation in Baoding urban area located in the central area of Beijing-Tianjin-Hebei region was analyzed,and the influencing factors of O₃pollution in Baoding urban area were discussed by constructing a Generalized Additive Model（GAM）,and a field investigation of plant O₃visible damage was carried out,to assess the degree of visible damage to wild plants by O₃stress in urban Baoding.Then,four groups of naturally growing peonies with different visible injury symptoms were used as the research objects,and the damage of leaf structure was identified by microscope,and the leaf pigment and root components were quantitatively analyzed.Finally,taking the rhizosphere soil of peony as the research object,the physical and chemical indexes,soil enzyme activities and microbial community composition of the rhizosphere soil of peony were quantitatively analyzed,and the key factors of the rhizosphere soil affecting the response of peony plants to O₃stress were discussed.The main research results are as follows.（1）From April to October in 2017-2019,O₃concentration in Baoding urban area was higher than the secondary standard limit of 160μg/m³for nearly 40%of the time.It was the primary air pollutant in Baoding urban area,and the high concentration period was mainly concentrated in April-September,which coincides with the growing season for native plants.And through GMA analysis,it was found that the influence of meteorological factors on the O₃concentration was greater than that of the main air pollutants（interpretation rate:70.60%>34.30%）,and the temperature represented by the daily maximum temperature was the main factor affecting the O₃concentration in the urban area of Baoding.Due to the serious O₃pollution in the urban area of Baoding,102 species of trees and shrubs near 6 national control points in Baoding urban area were surveyed on the symptoms of visible damage to O₃,and it was found that 49%of the species responded significantly to O₃stress,among which peony can be used as the characteristic of O₃damage.Indicator species,and the peonies in the same park showed different degrees of O₃visible damage symptoms.（2）4 groups of peony plants with different visible injury symptoms were selected（M1 is the yellow spot group,M2 is the yellow patch group,M3 is the brown patch group,and M4 is the normal group）.The tissue and chloroplast structure were damaged to different degrees,which was in line with the characteristics of O₃damage.It could be seen that the degree of damage was in the following order:M2≈M3>M1>M4,which further ensured the accuracy of the field survey results.With the decrease of visible damage,the content of chlorophyll and anthocyanin gradually increased,and the content of flavonoids gradually decreased.In addition,it was found that the differences in root components between groups were not significant,and there was no obvious nutrient deficiency in each group.（3）The water content of M4 and alkali hydrolyzable nitrogen in the rhizosphere soil physical and chemical indexes of peony plants in the four groups were the lowest,and there were significant differences among the available phosphorus groups.In addition,P element may also play a positive role in the damage of plant leaves.Among the extracellular enzymes in the rhizosphere soil,M4 had the highest activity related to carbon and nitrogen decomposition enzymes,and the highly active carbon and nitrogen decomposition extracellular enzymes may help plants resist O₃coercion.（4）The microbial community diversity in the rhizosphere soil of the four groups of peony was analyzed,and it was found that there was no significant difference in theαdiversity index of bacterial community among the groups,and the richness and diversity of the M4 fungal community were significantly lower than those of the other groups;bacterial communities and fungi The PCo A of the community showed that there were significant differences between M4 and the other three groups.In addition,the PCo A of the fungal community showed that the sample differences were consistent with the degree of damage seen in the samples（M2≈M3>M1>M4）,and the fungal community explained the sample differences.The rate was higher than that of the bacterial community（0.71>0.48）,indicating that the fungal community may respond more strongly to O₃stress.Based on the analysis of the composition of soil microbial communities in the rhizosphere of peony,it was found that the dominant bacterial communities were Actinobacteria,Proteobacteria,Chloroflex,and Acidobacteria.Norank＿f＿＿67-14、norank＿f＿＿Roseiflexaceae and others may assist the host against O₃stress;The dominant fungal communities were Basidiomycota,Mortierellomycota,Ascomycota.Penicillium,Beauveria,and Tomentella,which may inhibit the infection of pathogenic bacteria on plants.Geopora,unclassified＿f＿＿Thelephoraceae may help the host resist O₃stress.In summary,the antagonism or synergy that occurs between soil microbial communities and plant roots,as well as soil nutrient availability,indirectly affects plant growth.The leaves of peony plants showed different degrees of visible damage under O₃stress,which was indirectly feedback by rhizosphere soil physical and chemical indexes,soil extracellular enzyme activities and microbial community.The underground soil environment affected the ability of peony plants to cope with O₃stress.